With the compact-design discharge lamps such as the widely used compact fluorescent lamps, several solutions are known for connecting the electrode inleads of the discharge tube with the output terminals of the corresponding operating circuitry typically disposed in the base housing.
When choosing a specific solution for performing the electrical connection, it is a fundamental consideration that it is preferable to avoid using soldered or welded joints since in case of a printed circuit board with a high density of components, it is difficult to access such components and the assembly operation would be troublesome to be automated. In addition, the process of soldering or welding would exert a heat load that adversely affects the electronic circuitry. Further, in certain applications, solder materials of higher melting points would also be needed which, in addition to the fact that this would cause a heat load of intolerable extent, it would necessitate the use of some special flux material that could release vapors detrimental to health. Moreover, the flux material that has spilled would have to be removed later--an activity making the manufacturing process troublesome.
Those problems explained in the above make it obvious that a mechanical connection is the only solution deserving consideration.
Such a mechanical connection, i.e., a discharge lamp having mechanical connector components is described, e.g., in German Patent Specification No. DE 34 39 137. In this solution a contact pin is fixed in a contact holder part embedded in the electronic circuitry printed circuit board of a compact fluorescent lamp. In order to make electrical contact, the other end of such contact pin is pressed together with the electrode inlead of the discharge tube, into an accepting portion formed in the plastic base member of the compact fluorescent lamp. The electrode inlead and the contact pin are clamped one to another by the resilient force of the plastic side wall of the hole. It is known that plastic materials that can be used in mass products have poorer elastic properties than metals, and the elasticity of plastic materials even decreases as time elapses. This means that the solution according to the patent mentioned is unable to provide a sufficiently reliable contact between the electrode inleads and the output terminals of the electronic circuitry over the life of the product.
When choosing the type of solution for the mechanical joint, the material of the electrode inlead of the discharge tube should be considered, both in respect of its mechanical properties and its suitability for making electrical contact.
The solution according to the invention can be applied with advantage, e.g., in case of all types of the so-called compact-design discharge lamps having the electronic ballast in the base member, particularly in those having a printed circuit board carrying the electronic circuitry assembled in a crowded and hard-to-access way.